Historically, in commercially-used military gas generators for missiles, it has been conventional to employ electric circuits to create the time delays. Such arrangements, however, have distinct disadvantages a major one of which is short shelf life. The capacitors employed in the delay circuits tend to change characteristics over time, and this makes the gas generators unreliable vis-a-vis delay times.
It is known to use powders to generate time delays in gas generators. However, in one such device the chamber containing the delay powder was vented to the atmosphere so as to prevent the device from being fully sealed. Accordingly, and for other reasons, there was a tendency toward unreliability and lessened shelf life.
Another major disadvantage of the prior art was inability to achieve highly precise powder-column time delays in a gas generator for missiles.